Use of a metal ring‐marked catheter for geometric calibration in quantitative coronary angiography

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Abstract
Quantitative coronary angiography depends on accurate measurement of catheter shaft diameter for correction of X‐ray magnification errors. We compared the use of coronary catheters with a single metal ring (R), inserted during manufacture, with measurements using the edges of the catheter shaft (S) as a calibration mark. Both ring and shaft were 2.50 mm in diameter. On unmagnified X‐ray images, the ring measured 2.49 ± .040 mm, and the shaft measured 2.39 ± .040 mm in diameter. Quantitative coronary angiography using both ring and shaft for calibration provided the same percent stenosis (R: 72 ± 12; S: 71 ± 13), but stenosis cross‐sectional area was 28% different (R: 1.44 ± .24; S: 1.84 ± .34 mm2). Use of the catheter shaft for calibration causes overestimation of actual coronary artery dimensions. To prevent this problem, absolute measurements of coronary artery dimensions should be made with metal ring‐marked catheters.